>> However a bare spin_unlock_irq() in a function means that> callers which wish to keep interrupts disabled are subtly> subverted. We've had bugs from this before.>It is trivial to catch such bugs at runtime. I tried it a year ago, andimmediately run into sleep_on() users that legitimately callspin_lock_irq() with disabled interrupts. Perhaps they are gone now,I'll retest my patch.

> So the irqrestore functions are much more robust. I believe> that they should be the default choice. The non-restore> versions should be viewed as a micro-optimised version,> to be used with caution. The additional expense of the save/restore> is quite tiny - 20-30 cycles, perhaps.

OTHO, if a function doesn't work correctly if it's called with disabledinterrupts, then it should not use spin_lock_irqsave() - it'smisleading.e.g. if it calls kmalloc(GFP_KERNEL), down(), schedule(), etc.